1. Field of the Invention
This invention relates to a CDMA communication system for receiving a direct conversion CDMA radio wave signal having a plurality of antennas arranged for a space diversity receiving.
2. Description of the Prior Art
A CDMA (Code Division Multiple Access) communication system for receiving a direct conversion CDMA radio wave signal having a plurality of antennas arranged for a space diversity receiving is known. A diversity synthesis circuit for spread spectrum communication is disclosed in Japanese patent application provisional publication No. 6-14008. In such a prior art diversity synthesis circuit, a spectrum spreading signal is received by an antenna and is demodulated by a plurality of demodulators and the diversity synthesis circuit synthesizes the outputs of the demodulators. Moreover, "A Space-Path Hybrid Diversity Scheme for Base-Station Reception in CDMA Mobile Radio Communication Systems" is disclosed by Yoshio KARASAWA, Hisato IWAI, and Takayasu SHIOKAWA in TECHNICAL REPORT OF IEICE. A P93-29, SAT 93-12(1993-5) at pages 41-47 published by THE INSTITUTE OF ELECTRONICS, INFORMATION AND COMMUNICATION ENGINEERS. In that paper, a hybrid RAKE receiver for reducing multipath fading at a base station is disclosed which comprises N antennas, N correlators supplied with spreading codes, N Tapped Delay Lines with weighting functions, and a combining circuit, wherein the fading affection is reduced by the hybrid diversity (space diversity and the path diversity). FIG. 12 is a block diagram of such a prior art RAKE receiver.